1. Field of the Invention
The present invention relates to a method for producing capacitor-node contact plugs, and more particularly to a method for producing capacitor-node contact plugs in a DRAM (Dynamic Random Access Memory).
2. Description of the Prior Art
Prior semiconductor memory devices, for example the Dynamic Random Access Memory(DRAM), generally exist in the form of matrix, as shown in FIG. 1. In a semiconductor substrate with a T shape active region (AC), several parallel word lines (WL) arc formed. Next, on the sides of the word lines in the T shape region, source regions (S) and drain regions (D) are formed. Bit line contact pads (BC) are formed and coupled to an extend region (ED) of the T shape active region. A capacitor-node contact plug (CC) is coupled to the source region in turns. The extend region is the extension of the drain region. Bit lines are formed and coupled to the bit lines contact pads (BC), which are vertical to the word lines.
However, due to the trend for reducing the size of the DRAM, the contact area of the capacitor-node contact plugs with the landing pads or source regions in the lower layer is reduced. Because the capacitor-node contact plugs can touch the bit lines and the word lines easily, the formation of the capacitor-node contact plugs is more difficult, and the tolerance may not increase effectively.